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190               PRACTICAL ORGANIC CHEMISTRY

Reaction.—Add a drop of ferric chloride to the aqueous
solution of the aldehyde. A deep violet colouration is produced

f-Hydroxybensaldehyde.--Cc>\QUTL\tss needles, m. p. 115—116°;
scarcely soluble in cold water, readily in hot water, alcohol and
ether. Non-volatile in steam. The bisulphite of sodium
compound dissolves readily in water.

Reaction.—The same as above ; but the colouration is .less
intense. See Appendix, p. 297.

PREPARATION 84.
Salicylic Acid (0-Hydroxybenzoic Acid), QH4\co OH
Kolbe, / prakt. Chem., 1874, (2), 10, 95.
10 grms. caustic soda.
23     „     phenol.
This preparation should be commenced first thing in tlie
morning. Dissolve the caustic soda in about 10 c.c. of water In
a small porcelain basin and add the phenol. Heat the basin on
wire-gauze over a very small flarne, and, whilst holding it firmly
with a small clamp (tongs are too insecure), keep constantly
stirring with a glass rod. After a short time the mass becomes
stiff and balls together. The basin should now be removed
from the gauze, and the mass stirred and broken up as it cools.
When still warm, it is sufficiently hard to powder in a mortar.
It is quickly powdered and transferred to a small retort (200 c.c.)
heated in an oil or paraffin bath to 130—140°, and dried toy
passing over it a fairly rapid current of dry hydrogen from n.
Kipp. In about an hour all the moisture is removed, and trie
body of the retort appears dry. The light coloured mass in the
retort is allowed to cool whilst the hydrogen is passing throug'li,
then broken up and shaken into a mortar, when it is quickly
powdered and replaced. The object of the above operation is
to obtain perfectly dry, unchanged and well-powdered, sodiu.ni
phenate, upon which the success of the preparation entirely
depends. A moderate stream of carbon dioxide, dried throug'li
concentrated sulphuric acid, is now passed over the surface of